Inserter for minimally invasive joint surgery having interchangeable thread

ABSTRACT

An acetabular inserter ( 10 ) aids a surgeon in controlling the installation of an acetabular cup prosthesis ( 11 ) having a central, female aperture ( 13 ). The inserter includes an inserter head ( 20 ), a housing ( 12 ) and a locking mechanism. The housing ( 12 ) is attached to the inserter head, the housing enclosing a drive train ( 14 ) having, at a far end ( 134 ), a prosthesis engaging thread ( 124 ), and at the opposite end ( 42′ ), a handle ( 20 ) which facilitates turning of the drive train by the operator. The locking mechanism is associated with the housing which selectively locks the drive train, and thus the prosthesis, in position. The opposite end ( 42′ ) of the drive train has a latch device which enables quick removal from the housing for cleaning and sterilization.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. utility application Ser. No. 10/595,645 entitled INSERTER FOR MINIMALLY INVASIVE JOINT SURGERY, filed on May, 02, 2006, and claims priority to U.S. provisional applications of the same title, Ser. No. 60/746,061 filed on May 01, 2006, and Ser. No. 60/822,239, filed on Aug. 13, 2006, the contents of which are fully incorporated herein by reference and relied upon.

BACKGROUND OF THE INVENTION

This invention relates to surgical inserters such as impactors, for aiding in installing orthopedic prostheses, and, more particularly, to easily sterilizable inserters for installing acetabular implants in the acetabular socket.

Complicated mechanical devices have crevices and recesses that are difficult, if not almost impossible to clean with ease. Devices that are not properly cleaned and sterilized run the risk of disease transfer from patient to patient following the emergence of certain “prions” that are not killed by normal hospital sterilisation and need to be physically removed by washing/rinsing.

Further, in surgical procedures in which access to the treatment site is limited, it is difficult to use current solutions without subjecting the patient to repeated abrasion and tissue trauma when inserting and extracting surgical instruments.

Further, the insertion of the implant is often problematic, and the orientation of the implant, particularly any fixing holes that might be pre-drilled in the implant is often critical to minimize recovery time of the patient. Still further, once the appropriate position of the implant is selected, it is often difficult to ensure that the position does not change upon insertion of the assembly through the incision.

Still further, a surgical inserter is needed having an interface which engages with the particular prosthesis that the surgeon selects for the particular needs of the patient. Thus, for the surgeon to be able to position and insert a variety of prostheses, he must very often have a corresponding number of inserters, given that the interface is not standardized.

What is needed therefore is an inserter that is easily adjustable, disassembleable, and cleanable. Further, what is needed is an inserter that enables the surgeon to better maneuver position and install an implant in a particular angular orientation. Still further, what is needed is an inserter wherein the interface alone, and not the entire inserter, may be changed out to enable the interfacing with the most appropriate prosthesis without the need for having a special inserter on hand for each particular interface.

SUMMARY OF THE INVENTION

An acetabular inserter aids a surgeon in controlling the installation of an acetabular cup prosthesis generally having a central, female aperture. The inserter has a housing which supports a drive train having, at a far end, an interchangeable prosthesis engaging interface (e.g., an interchangeable thread), and at the opposite end, a handle which facilitates turning of the drive train by the operator.

The inserter enables easy and controlled orientation of a prosthesis attached to its end, which is important because the prosthesis often has pre-drilled holes and thus, these must be properly positioned prior to fastening through these holes. Proper positioning may be dictated due to different length fasteners to engage with bone of varying thickness.

An objective of the invention is to be “easily cleaned” by quick and modular disassembly which enables access to all surfaces so that they can be cleaned, the reduction in number of small radius internal corners, crevices and small gaps and the absence of blind holes.

Another object of the invention is to provide an inserter which enables the implant to be locked in an angular orientation prior to installation of the implant.

Another object of the invention is to provide a dual mechanism that uses common components to lock the implant in place as well as to provide for easy disassembly for cleaning and sterilization.

Another object of the invention is to reduce the number of pieces and the risk that parts could be lost.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawings represent, by way of example, different embodiments of the subject of the invention.

FIG. 1A is a cross-sectional side view of the inserter of the invention, including a side view of the drive train separated from the invention.

FIG. 1B is a side view of the inserter of the invention.

FIG. 1C is a perspective view of the inserter of the invention showing a one way catch mechanism.

FIG. 2A is an operational side view of the inserter of the invention.

FIG. 2B is an operational hack view of the inserter of the invention.

FIG. 3A is a perspective view of the inserter of the invention, showing a step of disassembly for cleaning.

FIG. 3B is a perspective view of the inserter of the invention, showing another step of disassembly for cleaning.

FIG. 3C is a perspective view of the inserter of the invention, showing a stage of disassembly for cleaning.

FIG. 3D is a perspective view of the inserter of the invention, showing a stage of re-assembly after cleaning.

FIG. 4A is a perspective view of the interchangeable interface of the invention, assembled together.

FIG. 4B is a close up perspective view of the interchangeable interface, disassembled.

FIG. 4B′ is a cross sectional view of the interchangeable interface.

FIG. 4C is a perspective view illustrating a first step of disassembly of an assembled interchangeable interface,

FIG. 4D is a perspective view showing the removal of the interchangeable interface, from a dove tail groove in the drive shaft assembly.

FIG. 5 is a schematic view of a prior art inserter.

FIG. 6 is a schematic view of the inserter of the invention in operation.

FIGS. 7A and 7B are perspective views of (A) the housing of the present inserter with an interchangeable inserter head attached, and (B) with an interchangeable inserter head removed

FIGS. 7C and 7D) respectively are cross-sectional and perspective views of an inserter head.

FIGS. 8A and 8B illustrate the manual removal and attachment of an inserter head to the inserter end of the housing of the present invention.

FIGS. 9A and 9B are (A) and assembled view and (B) an exploded view of an alternative inserter head disposed on the housing boss.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to FIGS. 1A-1C, an acetabular inserter 10 is provided to aid the surgeon in controlling the installation of an acetabular cup prosthesis 11 having a central, female aperture 13. The inserter 10 has a housing 12 which encloses a drive train 14 having, at a far end, a prosthesis engaging, interchangeable interface 16 (preferably having a prosthesis engaging thread), and at the opposite end, a handle 20 which facilitates turning of the drive train by the operator. The housing 12 may be C-shaped, as shown, in order to minimize the invasiveness of the surgery by better clearing anatomical structures and tissue.

The interface 16 is cut on a boss 22 which is releasably engageable with a linkage 24 which slides in an axial hole 26 in the housing 12. The interface 16 is preferably threaded. The piston 24 is connected by way of a first U-joint 30 to a lever 32 which slides in a pivoting sleeve 34 fixed to the housing 12 via a pivot 36. The lever 32 is connected via a second U-joint 40 to a second pivoting lever 42 which is fixed to pivot in a catch 44 on a pivot pin 46. The catch 44 is essentially a divot or a seat cut into the housing 12, against which the pivot pin 46 of the lever 42 is captured when a slide 50 is slide over the pin when engaged against the seat.

FIG. 1A includes a side view of the drive train of the invention. A slideable sleeve 52 slides over the lever 42 and has a trunion 54 to which a rod 56 is pivotally attached. The rod 56 passes through a one-way catch 60 in the housing 12. The one-way catch 60 can be a captured split wedge sleeve 62 having an inner diameter that just matches the outer diameter of the rod 56 and which is captured in a recess having a matching conical surface that surrounds the sleeve so as to allow the rod 56 to slide into the housing 12, but to prevent the rod from sliding out of the housing unless an unlock lever (not shown) is activated, such lever merely lifting the sleeve 62 out of engagement with the conical surface so as not to lock and to permit the rod to back out of the housing. Any number of alternative oneway lock devices may be used however, the selection of which being within the skill of a person of ordinary skill in this field.

Referring now to FIG. 1C, an alternative embodiment of the one way catch mechanism 60 is shown. In this embodiment, the rod 56 passes through a one-way catch 60 in the housing 12. The one-way catch 60 has an inner recess that matches the outer diameter of the rod 56. The inner recess has a ratchet pawl (not shown) that locks against one way ratchet teeth 67 so as to allow the rod 56 to slide into the housing 12, but to prevent the rod from sliding out of the housing unless an unlock lever 68 is activated, such lever merely pulling the pawl away from the teeth to permit the rod to back out of the housing.

A polymeric inserter head 64 is molded over the end of the housing 12, to absorb the impact stresses incurred during use of the inserter. The head 64 is selected so as to have good frictional characteristics as well. Nevertheless, a metal, non-molded head may also be used with satisfactory results.

Referring now to FIGS. 2A-2B, in operation, the interface 16 (preferably threaded) of the piston 24 is engaged with the hole 13 of the prosthesis 11. The operator may rotate the handle 20 about its axis to turn the drive train 14 in order to interface the piston 24 into the hole 13 of or to orient the prosthesis in what he believes to be a correct or an initial position. Then, an end 42′ of the lever 42 is urged downwardly toward the housing 12. Such downward movement acts through the drive train 14 to draw the piston 24 into the housing 12, and thus to cause the inner surface of the prosthesis 11 to be drawn against the head 64 so as to create a normal force between the inside of the prosthesis and the head so as to prevent rotation of the prosthesis 11 relative to the housing 12. The operator may use the one way locking mechanism 62 to lock tile lever 42 in a position so as to lock the prosthesis 11 against the head 64, thus enabling the surgeon to pre-set and lock the position of the prosthesis prior to the installation thereof. Note that orientation of the prosthesis 11 is important because the prosthesis often has pre-drilled holes 4 (shown in FIG. 4A) and thus, these must be properly positioned prior to fastening through these holes.

The “easily cleaned” objective of the invention enables access to all surfaces that they can be cleaned (parts covering another part can be moved or removed to expose all surfaces), the reduction in number of small radius internal corners, crevices and small gaps and the absence of blind holes.

Referring now to FIGS. 3A-3D, in the embodiment shown, the device 10 is disassembled for cleaning by simply sliding the slide 50 back so as to release the pivot 46 and then lift the drive train 14 out of the housing but allow it to remain pivotally connected at pivot 36. As the drive train 14 is pivoted, the piston 16 is drawn out of the hole 26 in the housing 12. To reassemble after cleaning, the piston 16 is reinserted into the hole 26 and the drive train 14 is rotated back into position, with the one way locking mechanism entering its receiver and the pivot 46 again entering into the catch 44. The slide 50 is then slide over the pivot 46 and the inserter 10 is again ready for use.

Referring now to FIG. 4A, the interchangeable piston 16 is shown joined to the drive train 14 so as to turn as a unit therewith across a bend through the universal joint 30. The piston 16 has an interface end 16′ that is preferably threaded with threads 124 to match the threads of a particular prosthesis 11. On an opposite end 16″ thereof, the piston 16 has a releasable connection mechanism 23 comprising a dove tail 25 (shown most clearly in FIGS. 4B and 4D) and a threaded ferrule 27.

Referring now to FIG. 4B, the dove tail 25 is formed so as to have a bulbous profile which slides into and mates with the linkage 24 which has a corresponding transverse aperture which cradles the dove tail 25 in such a way that once it is captured in the hole 26 in the housing 12. Note that the extreme ends 25′ of the dovetail 25 are cylindrical to provide surface contact in sliding with the hole 26.

Referring now to FIG. 4C, the piston 16 may be removed by unthreading the ferrule 27 by hand (for this purpose, the knurled annular portion 27′ is useful) so as to release a wedging force generated upon torquing the ferrule at assembly, the wedging force generated between the curved cylindrical walls of the aperture of the linkage 16 and the corresponding curved walls of the dove tail 25. Note, however, wedging is not required, but merely ensures an integral connection of the piston 16 to the linkage 24.

Referring now to FIG. 4D, after the torque is released, it s a perspective view showing the removal of the interchangeable interface, from a dove tail groove in the drive shaft assembly.

Referring to FIGS. 5-6, the inserter 115 and a prior art inserter 15, respectively, are shown passing through a miniature incision 35 in the patient's skin 30. In FIG. 5, the inserter 15 is shown approaching the acetabulum 40 in an orientation desirable to ream the socket 45. The difficulty with the prior art spindle 15 is shown as the shaft 3 impinges on the miniature incision 35 at edge of the incision 37. The current surgical protocols are being pushed to the limits and the incision sizes are being reduced in the hopes of increasing the patient's speed to recovery. In some cases surgeons are using a two-incision approach, one to reach the acetabulum and the other to reach the femur. Either one incision or two incision techniques demand less trauma to the patient requiring the instruments to be more optimally designed to make up for the lack of operating space. The reamer of FIG. 6 shows a new inserter 115, which has a bent housing 113 containing the drive shaft 107.

It is important to place the bends in the housing at critical locations to pass through the miniature incision without impinging on the skin 30 at 37 while still maintaining the same surgical protocol. The reason why the drive end 104 and the holding mechanism 120 need to be in line or on parallel axis is so that the applied force 130 results in an axial motion 140. This allows the surgeon to maintain the existing technique since inherently inserter 15 in FIG. 5 would give the same result since it has a straight drive shaft 3. This allows the surgeon to apply a load directly along the path of reaming.

It should be noted that a second head (not shown) can be mounted onto the front of the device 10, the head formed so as to conform with a surface of an acetabular cup liner, in order to enable the device to seat a liner as well as the cup.

The attached drawings represent, by way of example, different embodiments of the subject of the invention.

In operation, the prosthesis first is placed over or threaded onto the collet 120 via a threaded hole 122. In a second step, the prosthesis 11 is oriented with respect to the form of the inserter 10, in order to minimally impact soft tissue. In a third step, the handle 160 of the inserter 10 is gripped and the prosthesis 11 placed through the incision 35. In a fourth step, the inserter 10 is used to impact the prosthesis 11 in place by impacting a rear portion of the inserter with a mallet, for example. Optionally, with the current design, it is envisioned that the prosthesis 11 be inserted into the incision 35 as a first step, potentially taking advantage of being able to more freely maneuver it into the incision and to roughly position it prior to inserting the collet 120 of the inserter 10 into a mating hole in the tool head. If this optional procedure is used, the knob 20′ of the inserter may then be turned by the operator to actuate the opening of the collet 120 and thus the fixing on the end of the inserter 10. These optional steps substitute for the above mentioned four steps. In a fifth step, the knob 20′ is turned in an opposite direction in order to release the prosthesis 11. In a final step, the inserter 10′ is removed from the incision 35.

As noted above, in another preferred embodiment illustrated in FIGS. 7A through 9, the present inserter 10 has an inserted head 64 a that is removable and can be interchanged with an alternative inserter head that is configured to mate with a corresponding alternative prosthesis device 11. FIG. 7A illustrate this alternative embodiment with the interchangeable inserter head 64 a in place on the inserter end 80 of the housing 12 of the present inserter 10 in a fully assembled condition. In FIG. 7B, the inserter head 64 a removed from the inserter end 80 of the housing 12. FIGS. 7C and 70 are cross-sectional and perspective views inserter head 64 a showing a head recess 84 for closely receiving a housing boss 86 disposed at the inserted end 80 of the housing 12. A retainer means holds the inserter head 64 a in place on the housing boss 86 when it is attached to the housing 12. In the embodiment illustrated the retainer means comprises a detent groove 88 on the outer surface of the housing boss 86, and a snap ring 90 disposed in a ring groove 92 in the inner circumference of the head recess 84. In practice, when the housing boss 86 is initially received into the head recess 84, the snap ring 90 is forced into an expanded condition until the ring 90 snaps into the detent groove 88 on the outer surface of the housing boss 86 to hold the inserted head 64 a in place on the boss 86. As illustrated in FIGS. 8A and 8B, the inserter head 64 a is removed by manually pulling the head 64 a away from the boss 86 and overcoming the bias retaining the snap ring 90 in the detent groove 88.

FIGS. 9A and 9B are (A) and assembled view and (B) an exploded view of an alternative inserter head disposed on the housing boss. In the exploded view, an alternative interchangeable inserter head 64c is disposed at the inserter end 80 of the housing. The view is exploded to show the details of the components of a detent mechanism disposed on the housing boss 86.

The “easily cleaned” objective of the invention 10 enables access to all surfaces that they can be cleaned (parts covering another part can be moved or removed to expose all surfaces), the reduction in number of small radius internal corners, crevices and small gaps and the absence of blind holes.

In another advantage, it is simple to select a desired orientation of the prosthesis device 11, which enables the device to be locked in an angular orientation prior to installation. Additionally, due to the drawing of the prosthesis 11 against and in close contact with the inserter head 64, the contact between the two is robust as it made with minimal play or gaps there between, ensuring good support during impaction.

In an advantage, the inserter 10 is simple and easy to use, without complex and possibly confusing locks activated with the thumb. It is simple to select a desired orientation of the prosthesis 11.

In another advantage, due to the drawing of the prothesis 2 against the impaction head 40, the connection between the prosthesis 11 is robust as the connection is made without any play or gaps therebetween, ensuring good support during impaction.

An objective is to provide an inserter 10 that is easy to disassemble and for which the disassembly is easy to learn.

Another object of the invention is to provide a dual mechanism that uses common components to lock the implant in place as well as to provide for easy disassembly for cleaning and stelilization.

Another object of the invention is to minimise the number of pieces and the risk that parts could be lost.

The object of the invention is to provide an inserter 10 which enables the implant to be locked in an angular orientation prior to installation of the implant.

While one or more preferred embodiments of the present invention have been described, it should be understood that various changes, adaptations and modifications may be made without departing from the spirit of the invention and the scope of the appended claims. 

What is claimed is:
 1. An inserter for aiding a surgeon in controlling a prosthesis during installation of the prosthesis, the inserter comprising: (a) an inserter head; (b) a housing attached to the inserter head, the housing supporting a drive train having, at a far end, an interchangeable piston having a prosthesis engaging interface adapted for holding a prosthesis against relative axial movement therewith, and at the opposite end, a handling interface which facilitates engagement with a manipulator for turning of the drive train by the operator; and (c) a locking mechanism associated with the housing which selectively locks the drive train, and thus the prosthesis, in position, wherein further the drive train has a latch device toward the opposite end of the drive train, such device enabling quick removal of the drive train from the housing for cleaning and sterilization.
 2. The inserter of claim 1, wherein the housing has at least one bend permitting the housing to avoid anatomical structures or tissue during use in surgery.
 3. The inserter of claim 1, wherein the handling interface is a handle.
 4. The inserter of claim 2, wherein the drive train includes at least one u-joint located so as to transmit torque through the at least one bend in the housing.
 5. The inserter of claim 2, wherein the housing is C-shaped having at least two bends, in order to minimize the invasiveness of the surgery by better clearing anatoniical structures and tissue.
 6. The inserter of claim 1, wherein the drive train further includes a lever link which is supported by the housing so as to rotate on a fulcrum, such that, actuation of the lever link draws a threaded tip axially toward a distal end of the housing and, when connected to a prosthesis, draws the prosthesis against an impaction surface, wherein sufficient friction may be generated therebetween to lock a prosthesis in place.
 7. The inserter of claim 6, wherein the link lever has a knob attached to an extreme end thereof, the knob enabling a user to orient the tip.
 8. The inserter of claim 6, wherein a lockable, variable length link is attached between the link lever and the housing in order to permit a user to vary pressure that an attached prosthesis which is attached to the tip can exert against the impaction surface.
 9. The inserter of claim 8, wherein the variable link is infinitely variable and is unlockable via a latch (68) in order to permit release of pressure on the prosthesis.
 10. The inserter of claim 9, wherein the prosthesis engaging tip is connected by way of a first U-joint to a lever which slides in a pivoting sleeve fixed to the housing via a first pivot.
 11. The inserter of claim 6, wherein a one-way catch mechanism prevents a rod connected to the link lever from disengaging from the housing unless an unlock lever is activated.
 12. The inserter of claim 1, wherein the inserter head is covered by an inserter head covering, made of a shock-absorbing material, in order to absorb the impact stresses incurred during impaction of the inserter.
 13. A surgical kit including the inserter of claim 1, various pistons to fit different prostheses, a variety of prostheses, and a case to hold the inserter, pistons, and prostheses together in an organized fashion. 